As shown in FIG. 8, a grommet 505 is proposed to dispose a wire harness 503 to penetrate through a body panel 501 of an automobile. The periphery of the wire harness 503 illustrated in the figure is covered by a protective member 511 such as a protective tube or tape in a compartment outside part 507 and a compartment inside part 509 which are separated by a body panel 501. A large-diameter body part 513 of the grommet 505 is fitted within a through hole 515 of the body panel 501 watertightly. For the wire harness 503, while a space between the through hole 515 and the body part 513 is waterproofed, a space between the body part 513 and the wire harness 503 (that is, inside the grommet) is waterproofed.
The waterproofing inside the grommet is carried out by a waterproofing structure disclosed, for example, in PTL 1. That is, as shown in FIG. 9, waterproofing agent 519 is applied between the peripheries of electric wires 517. A waterproofing sheet 523 is wound around a waterproofing part 521 where the waterproofing agent 519 is applied so that the electric wires are bound into an electric wire bunch which has a circular section. Tapes 525 are wound around both ends of the waterproofing sheet 523. The wire harness 503 which has the waterproofing part 521 formed in this way is mounted to the grommet 505 by closely fitting the waterproofing part 521 in a wire harness through hole 514.
On the other hand, in the wire harness waterproofing structure in which a grommet is used, a solution which does not use the waterproofing agent 519 is proposed. For example, in the wire harness waterproofing structure disclosed in PTL 2, as shown in FIG. 10, a body part 513 of a grommet 529 is mounted to a through hole 515 of a dash panel 527 which separates an engine room and a compartment inside part, a long tube 531 is coupled to the body part 513, and the tube 531 is arranged inside the engine room which is the compartment outside part 507. The wire harness 503 in an unbound state is inserted through the body part 513 and inside the tube 531, and in this state, at least two throttle parts (a first fixed part 533 and a second fixed part 535) where the inside diameter of the tube 531 is narrowed down are provided at a position close to the distal end of the tube 531 and at a position which is spaced from the above position and near the body part. In the throttle parts, the inside diameter of the tube 531 is narrowed down by tightening fixing bands 537 to the periphery of the tube 531. By providing a flexed part 539 in the wire harness 503 drawn out from the grommet 529, the electric wires 517 are loosened.